MC gage experiment

[Farrell]

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Another way to do it is to simply weigh a sample piece of spruce. Using =
the electronic balance I use for action balancing work (goes to 0.01 =
grams), I simply weigh one or two 100 gram or so pieces of spruce to =
monitor when the weight, and hence MC, has stabilized. It may well be =
that the samples stabilize a bit quicker than the panel because of their =
smaller size, increased surface area and presumably more rapid rate of =
moisture equalization, so just give the panel a little extra time. And =
of course, like Ron N.'s excellent gauge, the samples would follow the =
panel around.=20

One nice thing beyond the weight monitoring method's simplicity is that =
you can use samples cut from the same stock you made the panel from. One =
potential hitch using wood that is not from your current panel stock is =
that the initial panel MC may be different from the gauge or whatever =
else you are using (here again, the width measurement method eliminates =
that potential problem). Let's say you have this very nice gauge that =
you had in your hot box a month ago and it has been sitting in your shop =
since then (should be pretty darn close to EMC in your shop - if you =
keep your shop at a constant RH). You get your spruce from where? =
Outside storage? The garage? Another tech in town? It may not be at the =
same EMC with the gauge in your shop. Now if you buy a three year's =
worth supply of spruce and store in inside your shop, perhaps you would =
be OK, but you would be surprised how long it takes for a big piece of =
lumber to come to an EMC with its environment - depending on how wet it =
was to begin with - many, many, many months. Bottom line, you just =
simply need to know what initial MC your wood is if you are using a =
gauge. You can do that reasonably well by drying in an oven and weighing =
(although I find the accuracy of this method to be a bit wanting).

David initially asked about quick drying methods. I think monitoring =
weight and/or panel width are fine methods, but I also think it is =
advisable to be patient and give the system a little extra time to be =
sure you have reached your target EMC. Employing two of these methods =
would be good insurance. If you are really trying to do this quickly - =
like you've got a tight production schedule - IMHO, you need a system =
like Ron O's and some real good, properly used, electronic equipment to =
accurately monitor the process. There is much known about kiln drying =
wood. If you want to keep it simple, and I think any low-volume shop can =
do that, you need to give a panel a week or two to dry and stabilize in =
most situations.

Terry Farrell

----- Original Message -----=20
From: "Ron Nossaman" <RNossaman@cox.net>
To: <davidlovepianos@earthlink.net>; "Pianotech" <pianotech@ptg.org>
Sent: Tuesday, November 11, 2003 12:03 AM
Subject: RE: MC gage experiment


>=20
> >Ron:
> >
> >I appreciate you offering this.  If I may just clarify what might =
seem
> >obvious.  Does this gauge, then, follow the panel around that you are
> >working on?  Once you have a reading for the size of your gauge at a
> >specific MC, do you simply put the gauge in the hot box with the =
panel and
> >when the gauge reads your target then it must be assumed that your =
panel
> >has also?  If that's the case, then I assume you take the gauge out =
when
> >the panel comes out and goes back in when the panel goes in.
> >
> >
> >David Love
>=20
>=20
> That's the idea. Instead of interpolating panel MC from the average of =

> repeated temperature and RH% measurements, I now have a direct MC% =
gage=20
> that responds at about the same rate as the in-progress panel. When =
the=20
> gage hasn't moved over a 24 hour period, I can reasonably assume the =
panel=20
> hasn't either, and I can thus be reasonably sure the panel MC is close =
to=20
> the reading taken from the gage. I like tools that make life simpler, =
and=20
> this is as idiot resistant a method of determining MC in a panel by=20
> independent but coexistent instrumentation as I've ever seen anywhere, =

> supplying a nearly 1:1 direct analog mirror of the panel reaction to =
humidity.
>=20
>=20
> Ron N

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